Stemming dummy for shooting coal



Sept. 2, 1941. F YAKES. JR 2,254,405

STEMMING DUMMY FOR SHOOTING COAL Filed March 29. 1940 INVENTH FLM/wf )f4/nfs, JR.

, A TORNEY Patented Sept. 2, 1941 omiso STATES TENT FFICE 'This invention relates to a stemming dummy for blasting operations and, while not limited thereto, is more particularly designed for use in breaking coal inv coal mines.'

The usual coal shooting operation consists of drilling orY boring a shot hole into the coal. These shot holes are of considerable depth, often up to twenty feet. The powder, dynamite, or other .explosive or expanding material isv then placed in the hole and forced to the far extremity thereof. The hole is then packed with material completely ftoY the breech. This packing is usually accomplished by placing stemming dummies or clay Ycartridges in the hole and tamping or packing them oompactly therein to prevent the force of the explosion from blowing` from the shot hole.

Such-a method requires considerable time to properly pack the stemming dummies in place and it also results in confining the force of the explosion to the immediate area around .the explosive. This concentration of the explosive action results in shattering and powdering the vcoal for a considerable area around the explosion and this shattered and powdered coal is svalueless.'

. .The principal object ofv this invention its to provideA a mechanically operated stemmingk vdummy which cangbeinserted into the open end of the shot hole vand quickly locked in place therein to Vvpreventthe force of the explosion from'blowing Afrom the hole.

One yadvantage of the improved stemming dummyis the entire length of the hole is used asl an expansion chamber so.y that` the force of the` explosion isV distributed, throughout theen, tire length thereof to givefa long uniform ex-#i I Vpanding action whichy will break down the coal in large chunks without the formation'of nes Another advantage is that thegtimev required to place'the usual stemming dummies in posiftion lis greatly reduced and the cost of the stemming dummies, Vwhich in the old systemV are Hentirely destroyed at each shot, is'eliminated for theimproved mechanical stemming dummy designed Yfor simplicity, Aeconolfhy,and efliciency.

,'lfhese, will rbecome more Yapparent from theioljf.

lowing description. l

In the 'following' detailed description 'Qf I .invention reference is had totheaccompanying drawing 'which "formsa'ipart hereof. Like nu- V55 merals refer to like parts in all views ofthe drawing and throughout the description.

In the drawing:

Fig. 1 is a side view of the improved dummy.

Fig. 2 is a longitudinal section therethr taken on the lin-e 2.2, Fig. 1.

Fig. 3 is a diagrammatic, vertical, sectional View through a typical coal seam, illustrating the position Yof the improved stemming dummy-ina shot hole therein. 1 Y

Fig. 4 is a detail cross section, taken onv'the line 1 -d, Fig. 2. Y "l The improved stemming dummy consistsofa stemming ugh,

cylindrical shankportion I0 terminating at one` extremity in -a .receiving socket ll andat its other extremity in ak pressure flange 12.'.Y A`

threaded draw boltV I3 extends throughout the length of the shank In and projects from both extremities thereof.. A tubular nut lll'having wrench faces I5 `is threaded on the threadedexe tremity of the draw bolt .and serves to clampY The other extremity of the draw boltr isy prop Avided with a head I8 which lrides againstaninf Y Ate'rnal shoulder in sleeve mrriloer I9. ',llesleevei member is provided withinclined openings 20 vwhich are directed towards the head 18. V-atl 0irltf ed head member 2l is threaded on'the sleeve mem-ber I 9 and close-s the outer extremity thereof.

A socketed ferrule 22 is placed upontheinner extremity of the sleeve member which isshoul- 1 Vdered to receive it. The socketed extremity Aof they .ierrule and the receiving-socket ll-on the shank la are of vthe samediameter and botnhare ia f larger diameter thanthe shank, sleeve and head portions. -1

An expansible rubber sleeve the draw bolt between the receiving socket AI I `and the ferrule 22. The rubber sleeve may be prol.vided with end Washers 24 if desired.

In Fig. 3 a typical coal seam is indicated at',r 25,YY in which a shot hole 2B has been drilled."V An exe plosive charge 2l isindicatedin place in Vthehole z at v2l* with its `electric ignition Wires Yprotruding therefrom at. 28. InNus'e, the stemming dummy 1 is forced in the hole suiciently farY tocausethe l sharpened fangs'll'toenterthe face ofthe coal about the hole 25,as illustrated inFig. 3. The wires 28 Vpass from ,ther hole through one'A-f' the spaces between "the of; the cross-,shaped Pressure Plate; c Y l" Y pointed Y 2351s placed aboutYV i v Y y The nut lll is now rotated to pull the draw bolt outwardly. The draw bolt cannot rotate with the nut due to the fact that it is provided with a longitudinally extending keyway 2Q into which a key 39, formed in the pressure plate IS, extends. The pressure plate cannot rotate since the prongs are engaged in the coal face.

The bolt pull-s the ferrule 22 against the rubber sleeve causing it to expand transversely against the walls of the shot hole with suicient force to prevent the dummy from being blown from the hole by the force of the explosion. It will be noted that the entire interior of the hole is open.

The shot is now red and the force of the eX- plosion acts throughout the entire interior of the hole to break down the coal throughout the entire length of the hole without wasteful shattering and powdering. It has been found that 26% less powder is necessary to produce the same or better breakdown than with ordinary tamped stemming.

After the shot is red the dummy is recovered from the fallen coal for reuse in another hole.

It is desired to call attention to the advantages of the relatively long, tubular nut I4. The nut protects the threads from damage at all times. The threads never project into the open at any time. The long nut with the wrench faces at the outer end is receivable in the chuck of an electric or air drill, with which most mines are provided for driving the auger bits and setting up.;nuts and bolts. The power drill can therefore be used for tightening the nut I4 and expanding the dummy.

The head member 2| receives the brunt of the p explosion and may be eventually worn away but it can be easily removed and replaced. It also allows easy access to the bolt for renewals and repairs. It will be noted that the force of the explosion against the head member is not transmitted to the draw bolt but is carried directly against the resilient sleeve 23 to still further expand and increase the holding capacity of the latter.

It was found by actual use of the invention under practical operating conditions that the stemming dummy would be thrown backward by the vforce'of ,the explosion with the breaking coal. This did not appear to interfere with the eiciency of the breaking action but in order to reduce the force of this back throw, to avoid damage to the dummy, the inclined openings 20 were placed in the sleeve member I9. The exact action of these openings is not fully understood but it was found that they practically eliminated all backthrow and the dummy simply falls with the coal at the point of use. It may be that the initial force of the explosion forces the sleeve down along the draw bolt against the resilient sleeve. tend to throw the dummy backward, but immediately the blast enters into the hollow interior of the sleeve and head through the openings 20 creating instantaneous pressure therein which snaps the sleeve forward under the head of the bolt to jerk the entire assembly back into place.

The point on the head member acts to spread the outwardly moving gases against the walls of the hole while the improved stemming dummy has been particularly designed, and successfully' used, for coal breaking work, it may be used wherever the material being broken is suiciently fragile t break before ejecting the dummy.

While a specific form of the improvement has been described and illustrated herein, it is de- This force might sired to be understood that the same may be varied, within the scope of .the appended claims, without departing from the spirit of the invention.

Having thus described the invention, what is claimed and desired secured by Letters Patent 1s:

1. An elongated stemming dummy for insertion in blasting shoe holes for sealing the latter against the force of an explosion comprising: a pressure plate for positioning over and about a shot hole; a draw bolt extending through said plate into said hole; an inner member on said draw bolt; a shank member extending inward from said plate toward said inner member; a resilient, longitudinally-compressible, laterallyeXpansible member about said bolt between the inner member and the shank member; a nut on said bolt exteriorly of said plate for drawing the inner member against the resilient member; and means for preventing rotation of the bolt in the pressure plate.

2. An elongated stemming dummy for insertion in blasting shot holes for sealing the latter against the force of an explosion comprising: a pressure plate for positioning over and about a shot hole; a draw bolt extending through said plate into said hole; an inner member on said draw bolt; a shank member extending inward from said plate toward said inner member; a resilient, longitudinally-compressible, laterallyexpansible member about said bolt between the inner member and the shank member; a nut on said bolt exteriorly of said plate for drawing the inner member against the resilient member; and means for preventing rotation of the bolt in the pressure plate; and means for preventing rotation of said plate with reference to the axis of said hole.

3. An elongated stemming dummy for insertion in blasting shot holes for sealing the latter against the force of an explosion comprising: a pressure plate for positioning over and about a shot hole; a draw bolt extending through said plate into said hole; an inner member on said draw bolt; a shank member extending inward from said plate toward said inner member; a resilient, longitudinally-compressible, laterallyexpansible member about said bolt between the inner member and the shank member; a nut on said :bolt exteriorly of said plate for drawing the inner member against the resilient member; a keyway in said bolt; and a key projecting from said plate into said keyway to prevent rotation of said bolt in said pressure plate.

4. An elongated stemming dummy for insertion in blasting shot holes for sealing the latter against the forceof an explosion comprising: a pressure plate for positioning over and about a shot hole; a draw bolt extending through said plate into Vsaid hole; an inner member on said draw bolt; a shank member extending inward from said plate toward said inner member; a resilient, longitudinally-compressible, laterallyexpansible member about said bolt between the inner member and the shank member; a nut on said bolt exteriorly of said plate for drawing the inner member against the resilient member; means for preventing rotation ofthe bolt in the pressure plate; and fangs projecting from said pressure plate into the wall material about said hole to prevent rotation of said plate about the "axis of said hole.

5. An elongated stemming dummy for insertion in'blasting shot holes for. sealing the latter tremity of said bolt. the latter resting against a v'said shank; a cylinder of compressible material about said bolt against the other end of said shank; and an inner member on the headed extremity of said bolt for compressing said resilient member against said shank.

6. An elongated stemming dummy for insertion in blastingvv shot holesl for sealing the latter against theforce of Yan explosion comprising: aY tubular shank member; a headed, threaded bolt passing through said shank member'and v extending from both yextremities thereof; a presthe headed extremity of said bolt, the latter resting against a shouldered recess therein; and a head member closing the inward extremity of said sleeve member.

7. An elongated stemming dumm'y for insertion in blasting shot holes for sealing the latter against the force of an explosion comprising: a

j tubular shank member; a'headed, threaded bolt passing through said shank member and extende ing from both extremities thereof; a pressure plate against one end of said shank member of a size to extend outwardly beyond the diameter of said hole; a tubular nut on the threaded extremity of said bolt clamping said plate against said shank; a cylinder of compressible material y' fabout said bolt against the other end of said shank; a sleeve member about the headed exshouldered recess therein; and a head member closing the inward extremity of said sleeve member, there being openings in said sleeve member to allow gases to pass to the interior thereof.

8. An elongated stemming dummy for insertion in blasting shot holes for sealing the latter against the force of an explosion comprising: a tubular shank member; a headed, threaded bolt passing through said shank member and extending from both extremities thereof; a pressure plate against one end of said shank member of a size to extend outwardly beyond the diameter of said hole; a tubular nut on the threaded extremity of said bolt clamping said plate against said shank; a cylinder of compressible material about said bolt against the other end of said shank; a sleeve member about the headed extremity of said bolt,

the latter resting against a shouldered recess therein; and a head member closing the inward extremity of said sleeve member; anda ferrule in said sleeve member for receiving the inner extremity of said cylinder of compressible material. i

9. An elongated stemming dummy for insertion in blasting shot holes for sealing the latter against the force of an explosion comprising: a tubular shank member; a headed, threaded bolt passing through said shank member and extend-,- ing from both extremities thereof; a pressure plate against one end of said shank member of a size to extend outwardly beyond the diameter of said hole; a tubular nut on the threaded extremity of said bolt clamping said plate against said shank; a cylinder of compressible material about said bolt against the other end of said shank; and an inner member on the headed ex-` tremity of said bolt for compressing said resilient member against said shank; pointed fangs on said pressure plate for preventing rotation thereof in said hole; and means for preventingV rotation of said bolt in said pressure platei f FRANK YAKES, J R. 

